An example of container transport devices such as one described above is disclosed in JP Publication of Application No. 2003-072917 (Patent Document 1). The container transport devices of Patent Document 1 are used to carry containers into, and out of, a storage facility for storing containers. And each container transport device includes a support member (vertically movable member 142) for supporting from below a container for holding semiconductor substrates. Three engaged portions (fitting engagement portions 8) are formed in the bottom surface of each container. And the support member has three positioning pins for engaging the engaged portions provided in the bottom surface of the container. The vertically movable member is configured to support a container with the container positioned in a supporting area by supporting the container from below with the three positioning pins engaged with the three engaged portions of the container.
Conventionally, FOUPs (Front Opening Unified Pod) specified by the SEMI (Semiconductor Equipment and Materials International) standards are often used as containers for holding semiconductor substrates. And the mainstream semiconductor substrates (wafers) held or carried by such containers used to be disk shaped substrates having a diameter of 300 mm. For this reason, the vertically movable member of the container transport device of Patent Document 1 described above has positioning pins that are so located to engage the three engaged portions formed in the FOUPs for semiconductor substrates having a diameter of 300-mm (referred to hereinafter as 300-mm FOUPs).
More recently, however, larger-sized semiconductor substrates (for example, disk-shaped semiconductor substrates of 450 mm in diameter) have been manufactured, in part, to improve productivity. Thus, it has become necessary for container transport devices to be able to transport large containers which are containers for holding larger-sized semiconductor substrates (for example, containers for 450-mm semiconductor substrates having a shape specified by the SEMI standards (referred hereinafter as 450-mm FOUPs)), in addition to the small containers (for example, above-mentioned 300-mm FOUPs) which are containers for holding smaller semiconductor substrates.
The aforementioned SEMI standards require that three groove-shaped engaged portions be formed in the bottom surface for both the 300-mm FOUPs and the 450-mm FOUPs. To be more specific, the bottom surface of a FOUP has three groove-shaped engaged portions, which are formed in the bottom surface of the container such that their longitudinal directions extend radially away from a reference position of the bottom surface of the container. And each of the separation distances between the reference position and each of the three engaged portions (referred to as second engaged portions) for the 450-mm FOUP is greater than the greatest of the separation distances between the reference position and each of the three engaged portions (referred to as the first engaged portions) for the 300-mm FOUP.